metamorphic
Greenschist
Greenschist (Chlorite Schist)
Hardness: 3.5-4.5 (Mohs); Color: Pale green to dark green; Luster: Pearly to vitreous on foliation planes; Crystal Structure: Monoclinic (microscopic); Cleavage: Perfect basal (schistosity); Specific Gravity: 2.7-3.0
- Hardness
- 3
- Color
- Pale green to dark green
- Luster
- Pearly to vitreous on foliation planes
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Physical properties
Hardness: 3.5-4.5 (Mohs); Color: Pale green to dark green; Luster: Pearly to vitreous on foliation planes; Crystal Structure: Monoclinic (microscopic); Cleavage: Perfect basal (schistosity); Specific Gravity: 2.7-3.0
Formation & geological history
Formed through regional metamorphism of mafic igneous rocks (like basalt) at low temperatures (300-450°C) and moderate pressures. It represents the 'greenschist facies' of metamorphism.
Uses & applications
Used primarily as decorative stone in landscaping, crushed stone for road construction, and occasionally for roofing or exterior walls due to its durability and distinct color.
Geological facts
The green color is primarily due to the presence of minerals like chlorite, epidote, and actinolite. It is a key indicator for geologists that the area underwent low-grade metamorphism typical of ancient mountain-building events.
Field identification & locations
Identify by its distinct greenish hue and 'schistose' texture (fine-grained, platiness). It is commonly found in metamorphic belts, such as the Appalachian Mountains or the Scottish Highlands. Collectors look for pieces with visible garnet or pyrite inclusions.
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